1. Field of the invention
The present invention relates generally to an improved wafer carrier for use in carrying a plurality of semiconductor wafers in a wafer processing environment, and more specifically Lo a wafer carrier which can effectively reduce the number of airborne particles which become attached to or deposit on a surface of the wafer which faces one end panel or wall of the carrier.
2. Description of the Related Art
As is well known in the art, IC (integrated circuit) fabrication consists of a variety of processing steps that add, alter, and remove thin layers in the selected regions. During the wafer processing, it is necessary to transport a plurality of wafers using a wafer carrier from one wafer processing station to another. Many of the water processing sequences for integrated circuits are Implemented in a clean room. However, it is impossible to completely prevent airborne particles from becoming attached to the wafers.
A wafer carrier has usually a rectangular box-like structure with no top cover and is provided with a plurality of grooves so as to vertically support a plurality of wafers in parallel at predetermined intervals.
With a conventional wafer carrier, attention has been paid to accommodating as many wafers as possible without preventing any contact between two adjacent wafers. However, the outermost wafers in the wafer carrier are well spaced from the corresponding carrier front and rear panels. This is because the location of each outermost wafer is not important in increasing the wafer transportation efficiency.
Japanese Patent (JP) Application No. 3-143523 which was laid-open under publication No. 4-36724, discloses a wafer carrier which is made of quartz and which is used for immersing the wafers into a processing bath filled with hydrogen fluoride (HF). This arrangement is directed to overcoming the problem caused by a wafer-exposed type carrier and which is therefore not provided with any front and rear panels (and also any side panels). During the processing of wafers using hydrogen fluoride, microscopic particles are released from the carrier and accumulate especially on lower horizontally extending structure bars which form part of the carrier. After immersion, the wafers are washed using clean water while being retained in the same carrier.
When the wafer carrier is rapidly immersed into the cleaning water, the microscopic particles tend to be washed off the upper portions of the lower supporting bars and float upwardly toward the wafer surface. These microscopic particles thus tend to become attached to the wafers.
In order to reduce this drawback, the above mentioned JP Application 3-143523 proposes to provide, in place of the lower supporting bars, a pair of end panels each of which has the same height as the wafer and is arranged in parallel with the wafers which are vertically supported in the carrier. That is, the fine particles tend to accumulate on the upper edges of the front and rear panels and accordingly, when the carrier is quickly immersed into the water, the contaminants (viz., microscopic particles) swiftly reach the water surface without traveling in the vicinity of wafers. Thus, the contaminants can be removed together with surface water.
It is understood that the above mentioned related art is irrelevant to reducing airborne particles which become attached to the wafer surfaces during transport.